Magnesium base alloy



Patented Jan. 13, 1942 moan-sum BASE ALLOY John McDonald, Midland,Mich., assignor to The Dow Chemical Company, Midland, Mich a corporationof Michigan No Drawing.

inthe structural. arts where a light weight metal is highly desirable,such as'for use in making castings, forgings, and'the like. However, theuse of these alloys in the rolled form to .make sheet metal articlesrequiring forming operations, such as bending and drawing, has notprogressed as rapidly due to the fact that, in general, alloys havinggood formability or ductility permitting relatively sharp bends to bemade without the article developing external cracks usually haveinferior characteristics as regards their tensile and yield strengths. 1

It is, accordingly, the principal object of the invention to provide amagnesium base alloy which can be made into rolled sheets and the likepossessing a suflicient degree of ductility or formability at ordinarytemperatures to be Application December 23, 1940, Serial No. 371,374

strengths coupled with satisfactory formability are manifest over theentire range of composi tion indicated, I have found that in general analloy containing from about 0.05 to 0.5 per cent of calcium, 1.5 to 2.5per cent of manganese, and from 3 to 8 per cent of thallium, possessesthe most satisfactory combination of properties. A particularlydesirable composition is one containing 0.15 per cent of calcium, 2 percent of manganese, and 5 per cent of thallium.

The following tablelisting some of the properties of rolled sheet metalmade from my new quaternary alloy and comparing these properties withthose of related ternary alloys, illustrates the improvement in strengthcharacteristics of my new alloy. over that of related commercial alloysand at the same time shows that the per Table Nominal composition percenAnnealed Cold rolled (remaindermagnesium) Percent Yield Tensile YieldTensile Ca Mn Tl elon tion strengthin strengthin strengthin strength ininfl chee lbsJsq. in. lbs./sq. in. lbs/sq. in. lbs./sq. in.

sharply bent, drawn, or otherwise shaped, while having highly improvedtensile and yield strengths.

Other objects and advantages will be apparent as the description of thisinvention proceeds.

My invention resides in the discovery that a magnesium base alloycontaining from 0.01 to 1 per cent of calcium, 0.01 to 3 per cent ofmanganese, and from 1 to 12.per cent of, thallium possesses theaforementioned desirable properties. The term magnesium used herein andin the appended claims is intended to include magnesium containing theordinaryimpurities found in the commercially pure metal, such as tracesof copper, silicon, nickel, and iron.

While the properties of high tensile and yield The properties set forthabove under the term annealed were obtained by first rolling specimensof the alloys at a temperature of 550 F.

and thereafter annealing them at various tem- A comparison of theproperties listed in the table shows that the yield and tensilestrengths in both the annealed and cold rolled state is markedlysuperior to those of related alloys, while it will be noted that the percent elongati on is only slightly inferior to that of the related alloysshowing the highest degree of formability.

The new alloy may be compounded by any of the methods usually employedfor melting and alloying metal with magnesium, such as by adding thealloying ingredients singly or jointly to a bath of molten magnesiumwhich is preferably protected from oxidation by a suitable flux. The

flux should be substantially free from magnesium chloride if the calciumcontent of the alloy is above 0.3 per cent. In those instances where thealloy is to be compounded containing less than 0.3 per cent of calcium,magnesium chloride may be present in the flux, but in this case it ispreferable to add the calcium last and without too much stirring andagitation to prevent loss of calcium into the flux.

It is to be understood that the invention is not limited to the specificcomposition herein described but may take other forms without departingfrom the scope of the invention.

I claim: A

1. A magnesium base alloy containing from about 0.01 to l per cent ofcalcium, from about 0.01 to 3 per cent of manganese, and from 1 to 12per cent of thallium, the balance being magneslum.

2. A magnesium base alloy containing from about 0.05 to 0.5 per cent ofcalcium, from 0.5 to 2.5 per cent of manganese, from 3 to 8 per cent ofthallium, the balance being magnesium.

3. A magnesium base alloy containing 0.15 per cent of calcium, 2 percent of manganese, 5 per cent of thallium, the balance being magnesium.

4. A magnesium base alloy containing from 0.01 to 1 per cent of calcium,about 0.01 to 3 per cent of manganese, and about 1 to 12 per cent ofthallium and characterized by improved tensile strength and yieldstrength as compared to a similar magnesium-calcium-manganese alloydevoid of thallium.

JOHN C. McDONALD.

